Elevation and windage knobs have long been an important part of a rifle scope. The elevation knob causes the optical axis of the scope to point slightly downwardly, so that the shooter will point the rifle up, relative to how it would otherwise be pointed for the same position of the reticle on a field of view. The windage knob performs the same function for azimuth, so that a shooter can compensate for the presence of a cross-wind. These knobs, however, do present shooters with some difficulties.
First, there is the problem always inherent in a mechanical linkage, of inaccuracy introduced by imperfections in the train of parts leading from the knob to the pivotably mounted optical element that is moved to adjust elevation and windage angle (collectively, “optical axis pointing angle”). There is an inevitable tolerance in each part, and some looseness in the system, which introduces uncertainty and inaccuracy into the pointing angle of the scope. These inaccuracies tend to be greatest at the far ends of the adjustment range. U.S. Pat. No. 6,862,832 does address this problem by introducing a system in which the pointing angle of the optical element is measured by an optical sensor. But neither this sensor, nor its mode of use, appears to be further described. Accordingly, the measurement accuracy provided cannot be determined. Further, it cannot be said that there is a thorough disclosure of implementation of a system with actual measurement of the optical element pointing angle.
Another problem encountered is that of knob over-rotation. Typically, both the elevation and windage knobs, in order to provide the shooter with both a full range and precision adjustment, can be fully rotated about three times. But this means that a shooter cannot determine, by simply viewing the knob, how far it has been rotated. Rather, he must remember how many rotations have been introduced. This can lead to a miss-adjustment, which that shooter might perceive only after missing a few shots.
Yet another problem is the need to leave shooting position to check pointing angle, either by removing one's eye from the scope ocular, or removing one's finger from the trigger to feel the knob position. Adjusting pointing angle is likely to cause an even greater interruption in the shot process.